Work machines utilize actuators for a number of applications. For example, fuel injectors, commonly used to deliver fuel to a combustion chamber in an internal combustion engine, utilize actuators. A fuel injector may deliver a certain quantity of fuel, which may be, for example, diesel fuel, to the combustion chamber in the engine at a certain time in the operating cycle of the engine. The amount of fuel delivered to the combustion chamber may depend on the operating conditions of the engine such as, for example, the engine speed and the engine load.
Precisely controlling the quantity and timing of the fuel delivered to each combustion chamber in the engine may lead to an increase in engine efficiency and/or a reduction in the generation of undesirable emissions. To improve control over the quantity and timing of fuel delivery, a typical fuel injection system includes an electronic control module that controls the timing and quantity of fuel delivered by a fuel injector. The electronic control module transmits a control signal to the fuel injector in the engine to deliver a certain quantity of fuel to the combustion chamber at a certain point in the operating cycle. The control module sends a signal to an actuator, typically a solenoid, of the fuel injector to control the quantity and timing of fuel injected. The control module can vary this signal in order to control the duration of solenoid activation and the control module can vary the magnetic force, or magnitude, created by the solenoid.
The solenoid controls the flow of high pressure activation fluid to the injector by opening and closing a high pressure inlet. The high pressure inlet receives a high pressure activation fluid from a high pressure supply, such as a high pressure rail, of the work machine. Typically, the solenoid controls the movement of a valve member controlling a high pressure inlet of the fuel injector. The valve member, in its first or closed position, prevents the flow of the high pressure activation fluid. When moved to a second or open position, the valve member allows the high pressure activation fluid to enter the injector. Activating the solenoid urges the valve member towards its open position, starting the injection cycle. The high pressure fluid acts within the fuel injector, causing injection of fuel to occur. Deactivating the solenoid ends the injection cycle and releases pressure caused by the high pressure fluid within the injector.
Most work machines utilize more than one combustion chamber and therefore require more than one fuel injector. The work machine typically operates most efficiently when the fuel injectors for each combustion chamber inject fuel for the same duration. Otherwise, the work machine may experience excessive power growth, greater emissions, and/or oil dilution problems. In addition, operating the fuel injectors in this manner may minimize engine noise, vibrations and harshness. To synchronize the fuel injectors within an engine, the control module has a preset profile for the fuel injectors correlating fuel quantity injected with solenoid activation duration. The amount of fuel delivered by the fuel injector depends on the movement of the valve member controlling the supply of the high pressure activation fluid. The faster or slower the valve member moves from its closed position to its open position varies the timing and amount of fuel delivered. Similarly, the amount of time the valve member takes to return to its closed position from its open position varies the timing and amount of fuel delivered.
However, no two fuel injectors perform in the same manner due to slight variations in mechanical tolerances during manufacture and the wear of components through use. This means that the same signal sent to different fuel injectors may result in a different quantity of fuel injected by each fuel injector. In addition, the timing and duration of injection may vary from injector to injector. Adjusting for these variations may improve fuel efficiency and/or reduce unwanted emissions. Typical solutions to these variations focus on understanding the valve member's motion.
U.S. Pat. No. 5,995,356 (“the '356 patent”) discloses a method to detect the movement of a solenoid-operated valve element. The '356 patent discloses activating a solenoid by sending current to the solenoid to urge a valve to its open position; then deactivating the solenoid so that the valve is urged towards its closed position. At a predetermined time after deactivating the solenoid, the current in the solenoid is measured to detect a predetermined characteristic change. This predetermined characteristic change corresponds to the valve having returned to its closed position. The '356 patent also discloses a circuit solution for measuring the current in the solenoid. This circuit is an example of a free-wheel circuit, where free wheeling means the circuit has a predetermined resistance so that when the energy which is stored in the solenoid is provide to the circuit, the current can be measured. The '356 patent, however, does not disclose how to use the information collected through the disclosed method.
Another characteristic of the movement of the valve member may also cause fuel injector inefficiencies. In some instances, the differences in the motion of the valve member as it moves from its closed position to its open position influences the timing and the amount of fuel injected into the combustion chamber. Eliminating or minimizing the variation in this opening motion from fuel injector to fuel injector may decrease differences in the fuel injection rate leading to an increase in fuel efficiency and/or reduction in unwanted emissions.
The method of the present disclosure solves one or more of the problems set forth above.